Research Activities

Development of visible Light Emitting Diodes (LED) and investigation of their physical characteristics and performance reliability (with Prof. R.Chikovani and V. Zorikov). 
  1. Diode emitting saturated Green light at 520-548 nm wavelengths range, to be used as etalon light sources in metrology at 532 nm. These devices were based on liquid phase epitaxial ternary compound of GaxAl1-xP [1, 2].
  2. Diode emitting Blue light at 460-505 nm wavelengths range, to be used as color sources for image information. These diodes were manufactured on the base chemical vapor deposited GaN epitaxial layers [3]. These efforts are supported by several patents issued in the former USSR, and also is several other countries [4]. 
  3. New matrix of opto-pairs based on CdS, CdSe photoresistors and GaN light emitting diodes on the same substrate [5]. 
Development of advanced dielectric films for Optoelectronic devices, insulators for Metal-Insulator-Semiconductor (MIS) and Metal-Insulator-Metal (MIM) capacitors (with Prof. Gadi Eisenstein)
  1. Multilayer optical filters (short, long and band pass) and antireflection coatings based on dielectric films applicable in a wide range of wavelength from visible to near infrared.
  2. U-type multilayer antireflection coating with reflectivities of less than 1X10-3 in a wide wavelengths range of ~150 nm [6]. 
  3. A wide class of high dielectric constant (high-k) insulator films of binary (such as Y2O3, Ta2O5, TiO2, Er2O3), ternary (such as AlHfO and HfTiO) and combination of new nanolaminate multilayer systems (Al2O3-TiO2, Al2O3-HfTiO, HfNO-SiO2-HfTiO) as prospective replacements to the conventional SiO2 gate dielectrics (easily tunneled by the injected carriers when their thickness scaled to 2 nm) in MIM and MIS structures and Non Volatile Memory (NVM) system with metallic nanocrystals as memory sites. The research efforts included the study structural, chemical and electrical characteristics of HfTiO based nanolaminate structures which have shown that they maintain amorphous state, low roughness, excellent interface properties and stability, while in contact with Si substrate, till 1000 oC of thermal processing. Effective Oxide thickness of less than 1.0 nm was achieved at low leakage current density and high breakdown electric field, which makes these layers compatible for a new generation of low power Complementary Metal-Insulator-Semiconductor based Very Large Integrated devices. This research has also shown that MIM devices based on this new kind of nanolaminate stack attain a record capacitance density of about 11-16 fF/ m2 with good linearity, temperature stability, low tangent loss and low dielectric constant dispersion with frequency [7-10].  
  4. MIS nonvolatile memory (NVM) capacitors (sensitive to illumination or temperature) and Field Effect Transistors based on single and two Gold and Platinum nano particle charge storage layers, SiO2 or HfO2 and a HfO2 or multi-layer HfNO/HfTiO tunneling and control insulators. The device exhibits an equivalent oxide thickness of 7.3 nm, a hysteresis of 10-15 V at a gate voltage of +11V to -8V with a storage charge density of 1.3x1013 and 2.75x1013 cm-2 respectively for single and double Gold and Platinum charge storage nanoparticles. A leakage of 2.3x10-6 and 3.6•10-5 A/cm2 at -10V, a breakdown voltage of 12.5 and 13.3V, was measured respectively for single and double gold charge storage structures.  A good retention property with a hysteresis window following more than 10 years of consecutive write/erase operations with a  7V swing were demonstrated. The capacitor characteristics are frequency independent for the 10kHz -1MHz range [11-17] and sensitive in the wide range of the wavele\ngths from Ultraviolet to the Infrared (280-800 nm)..
Development of a physical parameters extraction methods from Current-Voltage characteristics of semiconductor devices (with Prof. Gadi Eisenstein).
  1. A procedure for analyzing the experimental current-voltage characteristics of various types of semiconductor structures and devices, as an alternative to the conventional graphical methods is based on works of Dr. A.N. Zyuganov [18]. This procedure studies the power exponent parameter alpha=d[ln(J)]/d[ln(V)]  versus applied voltage characteristics and examines the peculiar regions (extremums, bends or asymptotes),  usually revealed in these curves, which are in turn  correlated to mathematical formalisms of known current transport mechanisms such as double injection, carriers hopping into trapping levels, thermionic emission of carriers over barriers and field ionization of trapping levels, respectively according to Schottky and Frenkel-Poole, Fowler-Nordheim tunneling of carriers through insulator and space charge limited current. This method of J-V characteristics analysis has been shown to be common to all types of MIM, MIS or P-N junction devices and may be facilitated to gain a better understanding of the charge transport nature as well as the limiting aspects of semiconductor and dielectric based device performance. 
  2. Validity of alpha-V method for the extraction of physical parameters such as ideality factor, barrier height, saturation current and shunt and series resistance in the cases of voltage dependent barrier height and linear or nonlinear series resistance in semiconductor P-N diodes (based on Si, InGaP and HgCdTe as well as of InGaAs/InGaAsP multiple quantum well and InAs/InP quantum dash laser structures) [19], and also the of Schottky and tunneling barriers, traps ionization energies and densities for MIM and MIS structures [20].  
  1. "The Green lambda=520-550 nm LEDs on GaAlP". Patent USSR, No. 4451273, 1990.
  2. T.V. Dzakhutashvili, V.M. Mikhelashvili, M.I. Saginuri, T.V. Skakun, and R.I. Chikovani, "LED Based on the GaAlP Epitaxial Layers Emitted at Wavelengths of 520-550 nm "Soviet Physics Semiconductors-USSR". 23 (12), pp. 1360-1362, 1989.
  3. A.N Zyuganov, V.V. Zorikov, V.M. Mikhelashvili, and R.I. Chikovani, "p-n Junction Inclusions in Gallium Nitride M-I-N Light-Emitting Devices", Soviet Technical Physics Letters, N7, n. 7, pp. 493-494, 1981.
  4. "Semiconductor Light Emitter Based on Gallium Nitride and Process for Manufacture Thereof", Patent of USA, No. 4.608.581, 1986.
  5. "The Method of Preparation of the Fast-Acting Optoelectronic Devices". Patent of USSR, No. 897064, 1980. 
  6. A. Bilenca, R. Alizon, V. Mikhelashvili, G. Eisenstein, R. Schwertberger, D.Gold, J.P. Reithmaier, A. Forchel, “InAs/InP  1550 nm Quantum-Dash Semiconductor Optical Amplifiers”, Electron. Lett., Vol. 38, pp. 1350-1352, 2002.
  7. V. Mikhelashvili, G. Eisenstein, F. Edelman, R. Brener, N. Zakharov and P. Werner “Electron Beam Evaporated Er2O3 as a High k Dielectric for Silicon” J. Appl. Phys. Vol. 95, pp. 613-620, 2004.
  8. V. Mikhelashvili, G. Eisenstein and A. Lahav, "High-k Al2O3-HfTiO Nanolaminates With Less Than 0.8 nm Equivalent Oxide Thickness", IEEE Electron. Device Lett., 28, pp. 24-26, 2006.
  9. V. Mikhelashvili, G. Eisenstein, "A High Capacitance Density MIM Structure Based on Al2O3-HfTiO Nanolaminate Stacks", Appl. Physics Lett., 90, 013506, 2007.
  10. V. Mikhelashvili, P. Thangadurai, W.Kaplan and G. Eisenstein, High capacitance density metal-insulator-metal structures based on a high- κ Hf Nx Oy -Si O2 -HfTi Oy laminate stack, Appl. Physics Lett., 92, 132902, 2008.
  11. V. Mikhelashvili, B. Meyler, S. Yofis, J. Salzman, M. Garbrecht, T. Cohen-Hyams, W.D. Kaplan, G. Eisenstein, "A nonvolatile memory capacitor based on Au nanocrystals with HfO2 tunneling and blocking layers",Appl. Phys. Lett. 95, 023104 (2009).
  12. V. Mikhelashvili, B. Meyler, S. Yofis, J. Salzman, M. Garbrecht, T. Cohen-Hyans, W.D. Kaplan, G. Eisenstein, "Nonvolatile memory capacitors based on double Au nanocrystals and HfO2 tunneling and laminate HfNO/HfTiO control high-k insulator layers layers", ECS Transactions, 25, 6, 465-471 (2009). 
  13. V. Mikhelashvili, B. Meyler, S. Yofis, J. Salzman, M. Garbrecht, T. Cohen-Hyams, W.D. Kaplan, G. Eisenstein, "A Nonvolatile Memory Capacitor Based on a Double Gold Nano-Crystal Storing Layer and High-k Dielectric Tunneling and Control Layers",   J. Electroch. Society, Vol. 157, No. 4, pp. H463-469, 2010. 
  14. V. Mikhelashvili, B. Meyler, M. Garbrecht , S. Yofis, Y. Salzman, T. Cohen-Hyans, W.D. Kaplan, Y. Roizin, M. Lisiansky, G. Eisenstein. "Optical properties of nonvolatile memory capacitors based on gold nanoparticles and SiO2-HfO2 sublayers", Appl. Phys. Lett.   98, 022905 (2011).
  15.  V. Mikhelashvili, B. Meyler, S. Yofis, Y. Shneider, A. Zeidler, M. Garbrecht , T. Cohen-Hyans, W.D. Kaplan,  M. Lisiansky, Y. Roizin, Y. Salzman, G. Eisenstein, "Nonvolatile low-voltage memory transistor based on SiO2 tunneling and HfO2 blocking layers with charge storage in Au nanocrystals", Appl. Phys. Lett.,  98, 212902 (2011).
  16. V. Mikhelashvili, 

    Y. Shneider, B. Meyler, G. Atiya, S.Yofis, T. Cohen-Hyams, W. D. Kaplan, M. Lisiansky, Y. Roizin, J. Salzman, and G. Eisenstein, "Non-volatile memory transistor based on Pt nanocrystals with negative differential resistance,"J. Appl. Phys., 112, 024319 (2012).


  17. V. Mikhelashvili, B. Meyler, Y. Shneider, S.Yofis, J. Salzman, G. Atiya, T. Cohen-Hyams, G. Ankonina, W.D. Kaplan, M. Lisiansky, Y. Roizin, and G. Eisenstein, "Ultraviolet to near infrared response of optically sensitive nonvolatile memories based on Platinum nano-Particles and High-k dielectrics on a SOI substrate", Journal of Applied Physics, 113, 074503 (2013).

  18. A.N. Zyuganov and S.V. Svechnikov, "Injection contact phenomenon in semiconductors, Naukova Dumka, Kiev. 1981 (in Russian).
  19. V. Mikhelashvili, G. Eisenstein, V. Garber, S. Fainleib, G. Bahir, D. Ritter, M. Orenstein, A. Peer, “On Extraction of Linear and Nonlinear Physical Parameters in Nonideal Diodes”, J. Appl. Phys., 85, p.6973-6983, 1999.
  20. V. Mikhelashvili, G. Eisenstein, “Effects on Annealing Conditions on Optical and Electrical Characteristics of Titanium Dioxide Films Deposited by Electron Beam Evaporation", J. Appl. Phys. 89, p. 3256-3269, 2001.


Project “Development of a Light-Emitting Device Based on Gallium Nitride and Investigation of its Electrical and Luminescent Characteristics” by V.Zorikov and V. Mikhelashvili was awarded as the best work on Complex Miniaturization of Radio-Electronic Devices for 1980, 

Nonvolatile memory capacitors based on double Au nanocrystals and HfO2 tunneling and laminate HfNO/HfTiO control high-k insulator layers layers

 J. Electroch. Society, Vol. 157, No. 4, pp. H463-469, 2010. 

Non-Volatile Low-Voltage Memory Transistors Based on SiO2 Tunneling and HfO2 Blocking Layers with Charge Storage in Au Nanocrystals.

Ultraviolet to near infrared response of optically sensitive nonvolatile memories based on Platinum nano-Particles and High-k dielectrics on a SOI substrate"

 Journal of Applied Physics, 113, 074503 (2013)